Electronically servo-assisted bicycle gearshift and related method

ABSTRACT

An electronically servo-assisted bicycle gearshift and method for electronically shifting the gears of a bicycle involves the steps of: receiving a signal requesting a displacement of a chain of a bicycle gearshift from a first sprocket to a second adjacent sprocket of a gearshift group comprising at least two sprockets; if the first sprocket has a smaller diameter than the second sprocket, obtaining an upwards gear-shifting position for the second sprocket, if the first sprocket has a larger diameter than the second sprocket, obtaining a downwards gear-shifting position for the second sprocket; and driving an actuator of the gearshift group to displace a guide element of the chain in an axial direction with respect to the gearshift group from the first sprocket to the upwards gear-shifting position for the second sprocket or to the downwards gear-shifting position for the second sprocket, respectively.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of Ser. No. 10/839,544filed May 5, 2004, which is incorporated by reference as if fully setforth.

BACKGROUND

The present invention concerns an electronically servo-assisted bicyclegearshift and a method for servo-assisting a bicycle gearshift, as wellas a program and an electronic circuit having means for carrying out themethod.

An electronically servo-assisted bicycle gearshift generally comprises arear actuator, a front actuator, a means for generating a signal, anelectronic control unit, a rear transducer and a front transducer. Therear actuator and front actuator each have a respective motor fordisplacing a chain through a guide element in an axial direction withrespect to a respective gearshift group. Each gearshift group comprisesat least two sprockets or toothed wheels associated with the hub of therear wheel (the sprockets also being called pinions and the chain guideelement also being called rear derailleur or simply gearshift) and,respectively, with the axis of the pedal cranks (the sprockets ortoothed wheels also being called crowns or gears and the guide elementalso being called front derailleur or simply derailleur). The chaindisplacement between sprockets takes place in a first direction (forexample from a sprocket with a smaller diameter to a sprocket with alarger diameter, or “upwards gear-shifting”) or in a second directionopposite to the first direction (for example, from a sprocket with alarger diameter to a sprocket with a smaller diameter or “downwardsgear-shifting”).

The means for generating a signal requests displacement of the chainfrom a first sprocket to a second adjacent sprocket of the respectivegearshift group, such as levers associated with the two handlebar gripsof the bicycle. The electronic control unit is connected to the rearactuator and to the front actuator, and operates, in a normal rideoperating mode (i.e. wherein the gearshift is controlled manually by therider or semi-automatically or automatically by the electronic controlunit), to receive the displacement request signal and drive the rear orfront actuator, respectively, based upon the displacement request signalto displace the chain from a first sprocket to a second adjacentsprocket of the respective gearshift group, based upon logic positions(“logic values”) representing the physical positions of the varioussprockets.

The rear transducer and the front transducer detects the position of theactuators (and therefore of the chain guide elements) and indicates theposition to the electronic control unit so that the actuators arestopped when the desired position has been reached.

Electronically servo-assisted bicycle gearshifts are described in U.S.Pat. Nos. 5,480,356; 5,470,277; 5,865,454; and EP 1 103 456, all ofwhich are assigned to Campagnolo S.r.l. and U.S. Pat. No. 6,047,230 andGerman patent application DE 39 38 454 A1.

In particular, EP 1 103 456 describes a gearshift comprising positiontransducers of the absolute type, capable of providing an electricalsignal indicating the absolute position of the derailleurs. Whenswitched on, such transducers take into account the actual position ofthe derailleurs, which could be slightly displaced due, for example, tovibrations caused by the travel of the bicycle.

In normal operation, in order to assist a gear-shifting from a firstsprocket to a second adjacent sprocket, sometimes it is not sufficientto displace the chain guide element (gearshift or derailleur) up to thesecond sprocket. In fact, due to the existing distance between the guideelement and the second sprocket that the chain must engage, and due tothe fact that the chain is at an angle during the gear-shifting, such amovement may interfere with the engagement of the chain on the secondsprocket. This is a serious problem when shifting gears.

The problem is particularly serious in the case of the front gearshift,where the chain is taut. To shift gears, in particular during an upwardsgear-shifting, the rear actuator or front actuator, respectively, mustbe displaced to a position typically beyond the position correspondingto the second sprocket. Such a displacement in advanced position withrespect to the second sprocket promotes the release of the chain fromengagement with the first sprocket and the engagement of the chain onthe second sprocket.

In mechanical control gearshifts, a control mechanism acts as anactuator to displace the chain guide element. The control mechanismcomprises a steel cable slidably contained in a sheath (“Bowden cable”)between a manual actuation lever and the chain guide element. Theactuation of the lever in a first direction applies a traction on thechain guide element through the steel cable, whereas the actuation ofthe lever in a second opposite direction applies a thrust on the chainguide element through the steel cable, or lets the cable and the chainguide element free to be returned by a return spring.

To make gear-shifting easier, some mechanical control gearshifts use acontrol system in which the actuation of the control lever causes thesteel cable to move by such a length that the chain guide element movesfurther than necessary to reach the position of the adjacent sprocket.When the control lever is released, the return spring acts to take thesteel cable—and thus the chain guide element—back to the positioncorresponding to the second sprocket. In other words, the actuation ofthe control lever causes a temporary displacement of the chain guideelement greater than the pitch between two adjacent sprockets of thegearshift group by a certain amount indicated hereafter as “overstroke.”

Such a mechanical control gearshift unfortunately has some drawbacks.First, it requires periodic and precise mechanical adjustment of boththe steel cable and the return spring tension. Second, it is possible toadjust the amount of the overstroke to only a single value, whichimpacts as much in all of the upwards gear-shiftings as in all of thedownwards gear-shiftings. Consequently, when the amount of theoverstroke in a gearshift group is adjusted for optimal gear-shifting inone direction (for example for upwards gear-shifting), a gear-shiftingin the opposite direction (in the example, downwards gear-shifting) isunsatisfactory. Alternatively it is necessary to adjust the amount ofthe overstroke to an intermediate compromise value, obtaining sufficientbut not optimal results in gear-shiftings in both directions.

In the case of the front gearshift group, upwards gear-shifting to theoutermost sprocket (the sprocket with the largest diameter) isdifficult. In this case even the provision of the overstroke may not besufficient to ensure that the chain engages correctly. Particularlyexperienced riders could avoid this by keeping the front derailleur atthe overstroke position for a certain amount of time (by holding thecontrol lever pressed). The time spent in overstroke position couldhowever be only determined “by ear” and/or “by sight” by the rider, withthe result that it could be too brief to give the desired result or solong as to cause harmful stresses to the mechanics of the gearshift oreven the arrangement of the chain in positions such as to causedangerous falls.

SUMMARY

The present invention seeks to overcome these problems using anelectronically servo-assisted bicycle gearshift and a method forservo-assisting a bicycle gearshift, as well as a program and anelectronic circuit having means for carrying out the method. The objectof the invention is to provide an electronically servo-assistedgearshift that allows optimal gear-shifting in both directions, up anddown, and between any pair of sprockets.

Specifically, the invention is a method for electronicallyservo-assisting an electronically servo-assisted bicycle gearshift (8),comprising the steps of:

-   -   a) receiving (101, 102) a signal requesting a displacement of a        chain (13) of a bicycle gearshift (8) from a first sprocket (11,        12) to a second adjacent sprocket (11, 12) of a gearshift group        (9, 10) comprising at least two sprockets,    -   b1) if (101) the first sprocket has a smaller diameter than the        second sprocket, obtaining (103) an upwards gear-shifting        position for the second sprocket,    -   b2) if (102) the first sprocket has a larger diameter than the        second sprocket, obtaining (104) a downwards gear-shifting        position for the second sprocket, and    -   c) driving (109, 110) an actuator (16, 17) of the gearshift        group (9, 10) to displace a guide element (14, 15) of the chain        (13) in an axial direction with respect to the gearshift group        (9, 10) from the first sprocket to the upwards gear-shifting        position for the second sprocket or to the downwards        gear-shifting position for the second sprocket, respectively.

BRIEF DESCRIPTION OF THE DRAWING(S)

FIG. 1 shows a perspective view of a bicycle equipped with anelectronically servo-assisted gearshift.

FIG. 2 shows a block diagram of the electronically servo-assistedgearshift.

FIG. 3 shows a block diagram of the method for electronicallyservo-assisting an electronically servo-assisted gearshift.

FIGS. 4-6 show different embodiments of front and rear memory means ofthe gearshift.

FIGS. 7-12 show different embodiments of overstroke memory means of thegearshift.

FIGS. 13-15 show different embodiments of gear-shifting memory means ofthe gearshift.

FIGS. 16-19 show different embodiments of an optional step of themethod.

FIG. 20 shows a flow chart exemplifying a mode selection of thegearshift.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

With reference to FIG. 1, a bicycle 1, in particular a racing bicycle,includes a frame 2 that defines a support structure 3 for a rear wheel 4and a fork 5 for a front wheel 6. A handlebar 70 is operativelyconnected to the fork 5.

The frame 2, at its lower portion, supports an axle of the pedal cranksor pedal unit 7, of the conventional type, to actuate the rear wheel 4through an electronically servo-assisted gearshift 8. The gearshift 8 issubstantially formed from a rear gearshift group 9 and a front gearshiftgroup 10. The rear gearshift group 9 includes a plurality of toothedwheels or sprockets or pinions 11 (FIG. 1 shows ten sprockets, but anynumber is possible, commonly nine or eleven) having different diametersand coaxial (axis A) with the rear wheel 4. The front gearshift group 10includes a plurality of toothed wheels or sprockets or crowns or gears12 (three in the illustrated example, but any number is possible,commonly two) that have different diameters and are coaxial (axis B)with the axle of the pedal cranks 7.

A looped transmission chain 13 selectively engages the sprockets 11 ofthe rear gearshift group 9 and the sprockets 12 of the front gearshiftgroup 10, to provide the different available gear ratios through theelectronically servo-assisted gearshift 8. The different gear ratios canbe obtained by moving a chain guide element or rear derailleur (or alsosimply gearshift) 14 of the rear gearshift group 9 and/or a chain guideelement or front derailleur (or also simply derailleur) 15 of the frontgearshift group 10.

The rear derailleur 14 and the front derailleur 15 are controlled by arespective actuator 16, 17 (FIG. 2) typically comprising an articulatedparallelogram mechanism and an electric motor with reducer to deform thearticulated parallelogram.

A position sensor of the rear derailleur or rear transducer 18 and aposition sensor of the front derailleur or front transducer 19 (FIG. 2)are associated with the actuators 16, 17. The details of theconstruction of the derailleurs 14, 15, of the respective actuators 16,17 and of the respective position sensors or transducers 18, 19 are notillustrated. Details of these can be found in the aforementionedpublished patent applications and patents. In particular, thetransducers 18, 19 are preferably of the type described in EP 1 103 456A2, suitable for providing an electrical signal indicating the absoluteposition of the derailleurs 14, 15.

An electronic power board 30, equipped with a battery, provides theelectrical power to the motors of the actuators 16, 17, to thetransducers 18, 19, to a microprocessors electronic control unit 40 andpreferably to a display unit 60. The battery is preferably of therechargeable type and the rear derailleur 14 can include, in a per seknown way, a dynamo-electric unit for recharging the battery.

In the present description and in the attached claims, an electroniccontrol unit 40 is a logic unit that can however be formed of manyphysical units, in particular of one or more distributed microprocessorswhich can be held in the display unit 60 and/or in the electronic powerboard 30 and/or in a command unit. While the program described herein ispreferably embodied in at least one microcontroller, alternatively itcan be stored in a computer memory or embodied in a read-only memory.

The electronic control unit 40 comprises, besides the microprocessor(s),a memory means that comprises one or more device(s) with severalfunctions: 1) storing the instructions that encode the managementprogram of the electronic gearshift; 2) temporary storing of servicevariables to carry out the program itself (registers); 3) volatile,non-volatile or permanent storing of some values specified later in thedescription. Regarding these values, the memory means are distinct inrear memory means, front memory means, overstroke memory means andgear-shifting memory means. It should be understood that such regionsare considered from the functional point of view and do not necessarilycorrespond to physically distinct storing devices. In other words, oneor more physical devices can be used for each of the memory meansindicated above or, vice-versa, each of the memory means indicated abovecan physically be embodied by a respective physical device or by memorylocations of one or more physical devices.

The storing devices can be of one or more types among read only, writeonce, or read/write, random access or sequential access memories, andthey can be made in various technologies, such as optical memories,magnetic memories, etc.

The storing device(s) can be contained in the display unit 60 and/or inthe electronic power board 30 and/or in the command unit and/or they canbe distinct devices.

The display unit 60 is preferably removable from the bicycle 1 andhouses at least part of the memory means of the electronic control unit40. The memory means housed in the display unit 60 stores the values setby the user for various parameters of electronic servo-assistedgearshift 8. This embodiment is particularly advantageous for racingbicycles, where the values set by the user reflect the know-how of therider and are therefore confidential. Also, it allows the display unit,which is relatively expensive, to be safeguarded.

The electronic power board 30 is, for example, housed in one of thetubes of the handlebar 70, in one of the tubes of the frame 2, forexample at a support for a drinking bottle (not illustrated), or in thedisplay unit 60, which is preferably housed centrally on the handlebar70.

The information transfer between the various components is carried outthrough electrical cables, advantageously housed inside the tubes of theframe 2, or else in a wireless mode, for example with the Bluetoothprotocol.

During travel, the rear and front derailleurs 14, 15 are controlled,through the actuators 16, 17, by the electronic control unit 40 basedupon signals requesting a displacement of the chain towards a sprocketadjacent to the one upon which the chain is engaged (upwards anddownwards gear-shifting request signals) established by manual commanddevices, or semi-automatically or automatically by the electroniccontrol unit 40 itself. The manual command devices can, for example,comprise levers 43, 44 associated with the brake lever 41 on a grip ofthe handlebar 70 for the upwards and downwards gear-shifting signals,respectively, of the rear gearshift group 9, and levers 45, 46 (FIG. 2)associated with the brake lever on the other grip of the handlebar 70for the upwards or downwards gear-shifting signals of the frontgearshift group 10 (the levers 45, 46 are not illustrated in FIG. 1 forthe sake of clarity).

As an alternative to the levers 43, 44 (45, 46), two manually operatedbuttons, or two buttons which can be operated by a swing lever can beprovided.

The electronic control unit 40 is also associated with the twotransducers 18, 19 to stop the motors of the actuators 16, 17 when therespective derailleur 14 or 15 has reached the desired position, suchthat the chain can engage the adjacent sprocket 11 or 12 (with a largeror smaller diameter, respectively) to the one that it engaged when thedisplacement request signal (upwards or downwards gear-shifting requestsignal, respectively) was generated through the manual command device43, 44, 45, 46 or by the electronic control unit 40. Such a position isindicated in the present description and in the attached claims as“gear-shifting position.” As shall be better explained hereafter, thegear-shifting position for at least one given sprocket 11, 12 of agearshift group 9, 10 is preferably different according to whether thegear-shifting is upwards or downwards and more preferably the upwardsand downwards gear-shifting positions are asymmetrically distant fromthe theoretical position of the sprocket.

In an alternative embodiment, the motors of the actuators 16, 17 arestepper motors which are driven by an appropriate number of steps foreach upwards or downwards gear-shifting and then automatically stopped,whereas the transducers 18, 19 are used to provide a feedback signal tothe electronic control unit 40 so that it can possibly provide toactuate once again the motors of the actuators 16, 17 in case thegear-shifting position has not been reached. This can, for example, bedue to the fact that the resisting torque offered by the derailleur 14,15, to some degree dependent upon how the rider is pedaling, was toohigh, greater than the maximum torque which can be delivered by thestepper motors.

More specifically, the electronic control unit 40 comprises a rearcounter 47 and a front counter 48. The counters 47, 48 can, for example,each be embodied by a register or a variable stored in a memory cell ofthe electronic control unit. The electronic control unit 40 in thenormal ride operating mode of the gearshift 8, drives the actuators 16,17 and tracks their position, increasing or decreasing the counters 47,48, for example by one unit for every step imposed on the stepper motorand/or based upon the reading of the transducers 18, 19.

According to some embodiments of the electronically servo-assistedgearshift 8, the memory means of the electronic control unit 40 comprise(FIGS. 4-6, described hereafter) rear memory means 49 for thetheoretical positions of the sprockets 11 of the rear gearshift group 9and front memory means 50 for the theoretical positions of the sprockets12 of the front gearshift group 10. The term theoretical positions ofthe sprockets 11, 12 means the values of the counters 47, 48 when thederailleurs 14, 15 are at the sprockets 11, 12.

In such embodiments of the electronically servo-assisted gearshift 8,the memory means of the electronic control unit 40 also compriseoverstroke memory means 51 (FIGS. 7-12, described hereafter) that storesat least one differential amount, indicated as “amount of overstroke.”The or each amount of overstroke represents the offset between thetheoretical position of the sprocket 11 and/or 12, indicated by thememory means 49 and/or 50, and the position that the guide element 14,15 must take up during an upwards and/or downwards gear-shifting toassist the gear-shifting itself, i.e. the upwards and/or downwardsgear-shifting position defined above.

The block diagram of FIG. 3 represents a method for electronicallyservo-assisting the gearshift 8 that generally applies both to the reargearshift group 9 and to the front gearshift group 10. If the chain 13is at a first sprocket 11 (12), block 100, and the counter 47 (48) has afirst logic value, when the rider actuates the manual upwardsgear-shifting request command 43 (45), block 101, or respectively, themanual downwards gear-shifting request control 44 (46), block 102 (orwhen such a request is generated by the electronic control unit 40itself), the electronic control unit 40 firstly provides for obtainingthe gear-shifting position for the second sprocket 11 (12), block 103 or104 respectively, that shall be an upwards gear-shifting position, ifthe first sprocket has a smaller diameter than the second sprocket(block 103), and a downwards gear-shifting position, if the firstsprocket has a larger diameter than the second sprocket (block 104). Asmentioned, the downwards gear-shifting position is preferably differentfrom the upwards gear-shifting position at least for one secondsprocket, and preferably such positions are asymmetrically distant fromthe theoretical position of the second sprocket.

Once the upwards gear-shifting position (block 103) or the downwardsgear-shifting position (block 104), respectively, has been obtained, theelectronic control unit 40 takes care of driving, block 109 or 110,respectively, the actuator 16 (17) to displace the chain along the axisA (B) in a first direction which goes from the first sprocket to thesecond sprocket until the counter 47 (48) reaches the value indicated bythe upwards gear-shifting position or by the downwards gear-shiftingposition, respectively.

In case the actuators 16, 17 comprise stepper motors, advantageously amovement of one step or an integer multiple of steps of the steppermotor, in a first or second direction of rotation, corresponds to eachunitary increase or decrease of the counter 47, 48. Following thedriving step, the electronic control unit 40 can optionally take care ofcarrying out a stay and repositioning step, schematically indicated bythe dashed blocks 111 and 112 in FIG. 3 and better described hereafterwith reference to FIGS. 16-19. Such a step comprises driving theactuator 16 (17) to displace the chain along the axis A (B) in the firstdirection or in a second direction opposite to the first direction untilthe counter 47 (48) reaches the theoretical position of the secondsprocket 11 (12), read directly from the memory means 49 (50) or derivedfrom the information read from the memory means 49 (50).

In these embodiments, the step of obtaining the upwards gear-shiftingposition (block 103), or respectively the downwards gear-shiftingposition (block 104), is carried out through the steps of:

-   -   obtaining, block 105 or 106, respectively, the theoretical        position of the second sprocket 11 (12) from the rear 49 (front        50) memory means, reading it directly from the memory means 49        (50) or deriving it from the information read from the memory        means 49 (50), as better specified hereafter;    -   where provided for, as better specified hereafter, algebraically        adding (block 107 and/or 108) the suitable amount of overstroke,        stored in the overstroke memory means 51, to the theoretical        position of the second sprocket 11 (12).

In a first embodiment (FIG. 4), the rear and front memory means 49 and50 are suitable for directly storing a value associated with eachsprocket 11, 12 of the respective gearshift group 9, 10, representingthe physical position of the sprocket 11, 12 in the respective gearshiftgroup. Thus, in the exemplifying case of rear gearshift group 9comprising ten sprockets or pinions 11, the rear memory means 49 aresuitable for storing several logic values: 1) a logic value R1associated with the wheel with the smallest diameter, 2) a logic valueR2 associated with the sprocket immediately adjacent to it, with aslightly larger diameter, 3) a logic value R3 associated with thesprocket immediately adjacent to it, with a yet larger diameter etc., upto a logic value R10 associated with the sprocket with the largestdiameter. For a front gearshift group 10 comprising three sprockets orcrowns 12, the front memory means 50 are suitable for storing a logicvalue F1 associated with the wheel with the smallest diameter, a logicvalue F2 associated with the sprocket with an intermediate diameter anda logic value F3 associated with the sprocket with the largest diameter.

In such an embodiment, the electronic control unit 40 obtains, in block105 or 106, the theoretical position of the second sprocket 11, 12 byreading the value associated with it directly from the memory 49, 50.

In a second embodiment (FIG. 5), the rear memory means 49 are suitablefor storing a differential amount associated with each pair of adjacentsprockets 11. Thus, in the exemplifying case of rear gearshift group 9comprising ten sprockets or pinions 11, the rear memory means 49 aresuitable for storing a differential amount ΔR1-2 associated with thepair consisting of the sprocket 11 with the smallest diameter and thesprocket 11 immediately adjacent to it (with a slightly largerdiameter), a differential amount ΔR2-3 associated with the pairconsisting of this latter sprocket and that one adjacent to it, etc., upto a differential amount ΔR9-10 associated with the pair of sprockets 11having the largest diameters; in the exemplifying case of frontgearshift group 10 comprising three sprockets or crowns 12, the frontmemory means 50 are suitable for storing two differential amount ΔF1-2and ΔF2-3. If the theoretical position of the sprocket with the smallestdiameter does not correspond to the zero value of the counter 47, 48,the front and rear memory means 49, 50 are also suitable for storingsuch a theoretical position R1, F1.

In such an embodiment, the electronic control unit 40 obtains, in block105 (or in block 106 respectively), the theoretical position of thesecond sprocket 11, 12 by adding (or subtracting) the differentialamount corresponding to the pair consisting of the first sprocket 11, 12and the second sprocket 11, 12 with immediately larger (smaller)diameter stored in the front and rear memory means 49, 50 to (or from)the current value of the counter when the chain 13 is at the firstsprocket, block 100.

As an alternative to the use of the current value of the counter atblock 100, in particular when the stay and repositioning step 111 (112)is absent, the electronic control unit 40 obtains, in block 105 (or inblock 106, respectively), the theoretical position of the secondsprocket 11, 12 by adding up the differential amount associated with thepair of sprockets formed by the second sprocket and the adjacentsprocket with a smaller diameter (which is the first sprocket in thecase of an upwards gear-shifting), all of the possible differentialamounts associated with the pairs of sprockets with smaller diametersand the value associated with the sprocket with the smallest diameter,if provided for.

In a third embodiment, which can be implemented when the gearshiftgroups 9, 10 comprise sprockets 11, 12 equally spaced by a certainpitch, the rear 49 and front memory means 50 (FIG. 6) store a singledifferential amount ΔR and AF. If the pitch between adjacent sprockets11 of the rear gearshift group 9 is equal to the pitch between adjacentsprockets 12 of the front gearshift group 10, there can be only a singlememory means, for example just the front memory 49. If the theoreticalposition of the sprocket with the smallest diameter does not correspondto the zero value of the counter 47, 48, the front and rear memory means49, 50 are also suitable for storing such a theoretical position R1, F1.In such an embodiment, the electronic control unit 40 obtains, in block105 (or in block 106, respectively), the theoretical position of thesecond sprocket 11, 12 by adding (or subtracting) the differentialamount ΔR or AF to or from the current value of the counter when thechain 13 is at the first sprocket, block 100.

Alternatively, the electronic control unit 40 obtains the theoreticalposition of the second sprocket 11, 12 from the product of thedifferential amount ΔR or ΔF times the number (j−1 if the secondsprocket is the jth of the gearshift group) of pairs of sprocketscomprised of the pair of sprockets formed by the second sprocket and bythe adjacent sprocket with a smaller diameter (which is the firstsprocket in the case of an upwards gear-shifting) and all of thepossible differential amounts associated with the pairs of sprocketswith smaller diameters and adding to this, if provided for, the valueassociated with the sprocket with the smallest diameter. (again, thisassumes that each sprocket is axially equidistant from its adjacentsprockets.)

Irrespectively of the embodiment of the front and rear memory means 49,50, various embodiments of the overstroke memory means 51 are possible.

According to a first embodiment (FIG. 7) just one value of overstroke Eis provided for, generally represented by a relative number. Theelectronic control unit 40 can use the single amount of overstroke E invarious ways according to the block diagram of FIG. 3. In a firstpreferred way, such an amount of overstroke E is algebraically added inthe case of an upwards gear-shifting, block 107, to the theoreticalposition of the second sprocket obtained in block 105 in the waysdefined above, whereas block 108 is absent; in such a case the amount ofoverstroke E is typically represented by a positive number.

In a second way, such an amount of overstroke E is algebraically addedin the case of a downwards gear-shifting, block 108, to the theoreticalposition of the second sprocket obtained in block 106, whereas block 107is absent; in such a case the amount of overstroke E is typicallyrepresented by a negative number so that its absolute value issubtracted from the theoretical position of the second sprocket.

In a third way, such an amount of overstroke E is algebraically added inthe case of an upwards gear-shifting, block 107, to the theoreticalposition of the second sprocket obtained in block 106, whereas in thecase of a downwards gear-shifting, block 108, its opposite (where −Xindicates the opposite of X) is algebraically added to the theoreticalposition of the second sprocket obtained in block 106. In such a casethe amount of overstroke E is typically represented by a positivenumber.

It should be noted that the amount of overstroke E, as well as thetheoretical position of the second sprocket 11, 12 stored directly orindirectly in the rear and front memory means 49, 50 and obtained inblock 105 or 106, shall have suitable values according to the way of useby the electronic control unit 40; typically, in the second and thirdways the theoretical position of the second sprocket can be correctedwith respect to the physical position of the sprocket itself.

Since the chain 13 is taut at the guide element 15 of the frontgearshift group 10, but not taut at the guide element 14 of the reargearshift group 9, to make the electronically servo-assisted gearshift 8and the method for servo-assisting it particularly simple, it can besufficient to provide for the algebraic adding steps 107, 108, and moreparticularly just the algebraic adding step 107 in the case of anupwards gear-shifting, only for the front gearshift group 10 or evenonly in the case of the gear-shifting towards the sprocket 12 with thelargest diameter of the front gearshift group 10.

According to a second embodiment (FIG. 8), the overstroke memory means51 are suitable for storing an amount E+ of overstroke for an upwardsgear-shifting and an amount E− of overstroke for a downwardsgear-shifting, in general represented by relative numbers. Moretypically, the amount E+ of overstroke for an upwards gear-shifting isrepresented by a positive number and the amount of overstroke E− for adownwards gear-shifting is represented by a negative number. In the caseof an upwards gear-shifting, the electronic control unit 40, in block107 of FIG. 3, algebraically adds the amount of overstroke E+ for anupwards gear-shifting to the theoretical position of the second sprocket11, 12 obtained in the step represented by block 105. In the case of adownwards gear-shifting, the electronic control unit 40, in block 108,algebraically adds the amount of overstroke E− for a downwardsgear-shifting to the theoretical position of the second sprocket 11, 12obtained in the step represented by block 106. Also in the secondembodiment, to simplify the electronically servo-assisted gearshift 8and the method for servo-assisting, it may be sufficient to provide forthe algebraic adding steps 107, 108 only for the front gearshift group10.

In a third embodiment, (FIG. 9), the overstroke memory means 51 aresuitable for storing a single amount of overstroke ER for the reargearshift group 9 and a single amount of overstroke EF for the frontgearshift group 10, each independently used by the electronic controlunit 40 in one of the three ways outlined above with reference to theembodiment of FIG. 7 and to which the other considerations outlined withreference to such a FIG. 7 apply. This is advantageous because thetension of the chain 13 is different at the guide elements 14, 15 of therear and front gearshift groups 9 and 10, because the pitch betweenadjacent sprockets 11, 12 of the rear gearshift group 9 can be differentfrom the pitch between adjacent sprockets 12 of the front gearshiftgroup 10, and because the distance between the guide element 14, 15 ofthe chain 13 and the sprockets 11, 12 is different in the case of thetwo gearshift groups, front 9 and rear 10. For the above reasons, it maybe suitable to differentiate the values of overstroke to be applied tothe rear gearshift group 9 and to the front gearshift group 10 asobtained by the third embodiment.

In a fourth embodiment (FIG. 10), the overstroke means 51 are suitablefor storing, for the rear gearshift group 9, an amount ER+ of overstrokefor an upwards gear-shifting and an amount ER− of overstroke for adownwards gear-shifting and, for the front gearshift group 10, an amountEF+ of overstroke for an upwards gear-shifting and an amount EF− ofoverstroke for a downwards gear-shifting, to be used in the waydescribed above with reference to the embodiment of FIG. 8.

The amounts of overstroke according to this fourth embodiment ER+, ER−,EF+, EF− are also generally represented by relative numbers, buttypically the amounts ER+, EF+are represented by positive numbers sothat their absolute value is added to the theoretical position of thesecond sprocket 11, 12, whereas the amounts ER−, EF− are represented bynegative numbers so that their absolute value is subtracted from thetheoretical position of the second sprocket 11, 12. This is because, toassist the gear-shifting from a first sprocket to a second sprocket, itturns out to be suitable to displace the chain guide element 14, 15 in agear-shifting position far from the first sprocket beyond the secondsprocket.

According to a fifth embodiment, the overstroke memory means (FIG. 11)store an amount ERj of overstroke for each sprocket of the reargearshift group 9 and an amount EFj of overstroke for each sprocket ofthe front gearshift group 10. The amounts of overstroke ERj, EFj can bemanaged by the electronic control unit 40 in block 107 and/or in block108 in the three ways described above with reference to the embodimentof FIG. 7. If the first way is used, in which in the case of an upwardsgear-shifting the amount of overstroke ERj or EFj associated with thesecond sprocket is algebraically added, in particular added in anabsolute value, to the theoretical position of the second sprocket,whereas block 108 is absent, no amount of overstroke associated with thesprocket with the smallest diameter shall be provided for; if the secondway is used, in which in the case of a downwards gear-shifting theamount of overstroke ERj or EFj associated with the second sprocket isalgebraically added, in particular subtracted in an absolute value, tothe theoretical position of the second sprocket, whereas block 107 isabsent, no amount of overstroke associated with the sprocket with thelargest diameter shall be provided for.

According to a sixth embodiment, the overstroke memory means (FIG. 12)store an amount of overstroke for an upwards gear-shifting ER+j, EF+jand an amount of overstroke for a downwards gear-shifting ER-j, EF-j foreach intermediate sprocket 11, 12 of each gearshift group 9, 10, as wellas an amount of overstroke for an upwards gear-shifting ER+j, EF+j forthe sprocket with the largest diameter and an amount of overstroke for adownwards gear-shifting ER−1, EF-1 for the sprocket with the smallestdiameter. From another point of view, an amount of overstroke for anupwards gear-shifting and an amount of overstroke for a downwardsgear-shifting are stored for each pair of adjacent sprockets of eachgearshift group. Thus, in the case of rear gearshift group 9 having tensprockets 11, eighteen amounts shall be provided for and in the case offront gearshift group 10 comprising three sprockets 12, four amountsshall be provided for.

The electronic control unit 40, in block 107 of FIG. 3, algebraicallyadds the amount of overstroke ER+j, EF+j for an upwards gear-shiftingassociated with the second sprocket to the theoretical position of thesecond sprocket 11, 12; in the case of a downwards gear-shifting, theelectronic control unit 40, in block 108, algebraically adds the amountof overstroke ER-j, EF-j for a downwards gear-shifting associated withthe second sprocket to the theoretical position of the second sprocket11, 12.

It is worth highlighting that in all of the embodiments of theoverstroke memory means 51 described above, it is possible to choosebetween the implementation of an adding operation in blocks 107, 108associated with the storing of relative numbers in the memory means 51,and the implementation of adding operations in block 107 and subtractionoperations in block 108 associated with the storing of typicallypositive, but also relative, numbers in the overstroke memory means 51.The upwards gear-shifting position obtained in block 103 is generallydifferent from the downwards gear-shifting position obtained in block104, because it is obtained through a different application of a sameabsolute overstroke value in the aforementioned two blocks, because itis obtained through the application of the or an overstroke value injust one of the aforementioned blocks, or because it is obtained throughan analogous application of different overstroke values in theaforementioned two blocks. Even more preferably, the upwards anddownwards gear-shifting positions are asymmetrical about the theoreticalposition of the second sprocket, like in the latter two cases.

According to other embodiments of the electronically servo-assistedgearshift 8, the electronic control unit 40 comprises gear-shiftingmemory means 52 instead of the overstroke memory means 51.

For example, in a first embodiment (FIG. 13), the gear-shifting memorymeans 52 also replace the front memory means 49 and the rear memorymeans 50 and are suitable for directly storing an upwards gear-shiftingposition R+j, F+j and a downwards gear-shifting position R-j, F-j foreach intermediate sprocket 11, 12 of each gearshift group 9, 10, as wellas an upwards gear-shifting position R+j, F+j for the sprocket with thelargest diameter and a downwards gear-shifting position R−1, F−1 for thesprocket with the smallest diameter.

In other words, the gear-shifting memory means 52 are suitable forstoring the upwards gear-shifting position towards each sprocket 11, 12,apart from the sprocket with the smallest diameter, and the downwardsgear-shifting position towards each sprocket 11, 12, apart from thesprocket with the largest diameter. Therefore, two (different)gear-shifting positions correspond to each non-end sprocket 11, 12 ofthe rear or front gearshift group 9, 10, according to whether thesprocket 11, 12 is reached during an upwards gear-shifting or during adownwards gear-shifting. One gear-shifting position, upwards ordownwards respectively, corresponds to each end sprocket 11, 12 of thegearshift group, i.e. those with the largest and the smallest diameter.

In FIG. 13, the gear-shifting memory means 52 are suitable for storingthe nine upwards gear-shifting positions R+2, R+3, . . . , R+j, . . . ,R+10 and the nine downwards gear-shifting positions R−1, R−2, . . . ,R−i, . . . , R−9, as well as the two upwards gear-shifting positionsF+2, F+3 and the two downwards gear-shifting positions F−1, F−2. (Thenumber of sprockets is not limiting, that is, other numbers of upwardsand downwards gear-shifting positions may be suitable, according to thenumber of sprockets.)

In the method for servo-assisting a gearshift 8 according to thisembodiment, in blocks 103 and 104 the electronic control unit 40 obtainsthe gear-shifting positions, namely the values that the counters 47, 48must take up so that the derailleurs 14, 15 are in positions such as toallow the engagement of the chain 13 with the sprockets 11, 12 desiredfrom time to time, by reading the suitable value directly from thegear-shifting memory means 52.

Similarly to what stated when dealing with the overstroke memory means51, the upwards gear-shifting positions, or preferably the downwardsgear-shifting positions, could coincide with the theoretical positionsof the second sprockets 11, 12 since these positions can cause asufficient displacement of the chain 13 to obtain the gear-shifting.

In other embodiments of the gearshift 8, the electronic control unit 40comprises the rear and front memory means 49, 50 in one of the variousembodiments described above (FIGS. 4-6) and, in the gear-shifting memorymeans 52, just the upwards gear-shifting position (FIG. 14) or just thedownwards gear-shifting position (FIG. 15), respectively, for eachsprocket apart from the sprocket with the smallest or largest diameter,respectively. In such embodiments, the step of obtaining the upwardsgear-shifting position (block 103) or the step of obtaining thedownwards gear-shifting position (block 104), respectively, shall becarried out by reading the value directly from the gear-shifting memorymeans 52, whereas the step of obtaining the downwards gear-shiftingposition (block 104) or the step of obtaining the upwards gear-shiftingposition (block 103), respectively, shall be carried out through thestep, block 106 or block 105 respectively, of obtaining the theoreticalposition of the second sprocket from the front and rear memory means 49,50.

Moreover, analogously to what has been indicated with reference to theembodiments providing for the overstroke memory means 51, in embodimentsproviding for the gear-shifting memory means 52 in combination with thefront and rear memory means 49, 50, the upwards and downwardsgear-shifting positions, respectively, can be provided for not all ofthe sprockets, but only for the sprockets in which a gear-shiftingposition which is different from the theoretical position is necessary.In particular, in the gear-shifting memory means 52 according to theembodiment of FIG. 14, just the upwards gear-shifting position for thesprocket 12 with the largest diameter of the front gearshift group 10could be provided for.

The embodiments of FIGS. 13-15 have the advantage of requiring littlememory and of not requiring algebraic adding operations by theelectronic control unit 40. However, to implement the optional step ofstay and repositioning illustrated by blocks 111, 112 and describedhereafter, it is necessary to provide for the front and rear memorymeans 49, 50 to store the theoretical positions, which in the case ofthe embodiment of FIG. 13, reduces the advantage of the little memoryrequired.

Embodiments in which the gear-shifting positions are stored asdifferential amounts, analogously to the embodiments of FIGS. 5 and 6,are also possible.

It can easily be understood that, for a specific electronicallyservo-assisted gearshift 8, the values of the gear-shifting positionsstored in the gear-shifting memory means 52 differ from the values ofthe theoretical positions by an offset that would correspond to the orthe respective amount of overstroke in one of the embodiments providingfor the overstroke memory means 51. In other words, the values of thegear-shifting positions stored in the gear-shifting memory means 52 inuse encompass the amount or amounts of overstroke.

It is possible to use different embodiments of the memory means, and/ordifferent ways of using the amounts of overstroke stored in theoverstroke memory means 51, for the rear gearshift group 9 and for thefront gearshift group 10.

As mentioned, the method for servo-assisting a bicycle gearshift canprovide, after the guide element 14, 15 of the chain 13 has been takeninto the gear-shifting position at blocks 109, 110, for an optional stepof stay and repositioning, schematically represented by block 111 and/orby block 112 of FIG. 3. In the optional step of stay and repositioning111, 112, the electronic control unit 40, once a certain period of timehas elapsed and/or once an end-of-gear-shifting-request signal has beenreceived, as better explained hereafter, drives (in a step indicated byblock 116 in FIGS. 16-19) the actuator 16, 17 to displace the chain 13until the counter 47, 48 reaches the theoretical position of the secondsprocket 11, 12, obtained from the memory means 49, 50 in the waysdescribed above with reference to blocks 105, 106.

It should be understood that the displacement shall take place along theaxis A, B in the first direction from the first sprocket to the secondsprocket or more typically in the second direction from the secondsprocket to the first sprocket according to the amount of overstroke or,in the case of the embodiments of FIGS. 13-15, according to whether theupwards gear-shifting position is smaller or greater than thetheoretical position of the second sprocket, or the downwardsgear-shifting position is greater or smaller than the theoreticalposition of the second sprocket.

The advisability of providing for such a step of stay and repositioning111, 112 consists in that even providing for a gear-shifting positionwhich is different from the theoretical position of the second sprocket(where the difference in position or offset is stored in the overstrokememory means 51 or in any case encompassed in the values of thegear-shifting positions stored in the gear-shifting memory means 52) maynot in itself be sufficient to cause the chain 13 to correctly engagewith the second sprocket 11, 12.

As mentioned in the Background above, the problem is particularlyserious in the case of upwards gear-shifting towards the sprocket 12with the largest diameter of the front gearshift group 10 (the outermostone). With the mechanical control gearshifts equipped with overstrokedescribed, skilled riders could avoid this by maintaining pressure onthe control lever and thus the derailleur 14, 15 at the gear-shiftingposition for a certain amount of time. The time of stay in gear-shiftingposition could however only be determined “by ear” and/or “by sight” bythe rider, with the result that it could be too brief to give thedesired result or so long as to cause harmful stresses to the mechanicsof the gearshift or even the arrangement of the chain in positions suchas to cause dangerous falls.

In a first embodiment of the step of stay and repositioning 111, 112,illustrated in FIG. 16, the aforementioned step of driving the actuator16, 17 to displace the guide element 14, 15 of the chain 13 in thetheoretical position of the second sprocket 11, 12 (block 116) issubordinated to the passing of a predetermined period of time after thestep 109, 110 of driving the actuator 16, 17 to displace the guideelement 14, 15 of the chain 13 in the gear-shifting position.

More specifically, the electronic control unit 40 takes care, in block113, of activating a timer and, in block 114, of monitoring the passingof a predetermined time period T. The timer can, of course, be acount-down or a count-up one and can be implemented by a memory variablemanaged by the clock signal of a microprocessor of the electroniccontrol unit 40 or by a dedicated device.

When the predetermined time period T has passed, if necessary in a block115 a step of obtaining the theoretical position of the second sprocket11, 12 from the information stored in the front and rear memory means49, 50 is carried out and then, in block 116, the aforementioned step ofdriving the actuator 16, 17 to displace the chain 13 until the counter47, 48 reaches the theoretical position of the second sprocket 11, 12 iscarried out. It should be understood that the step 115 of obtaining thetheoretical position of the second sprocket 11, 12 is indicated asoptional since typically it will not be carried out if said theoreticalposition had already been obtained previously when carrying out the steprepresented by block 105, 106.

In a second embodiment of the step of stay and repositioning 111, 112,illustrated in FIG. 17, the aforementioned step of driving the actuator16, 17 to displace the guide element 14, 15 of the chain 13 in thetheoretical position of the second sprocket 11, 12 (block 116) issubordinated to the receiving of an end-of-displacement-request signalafter the step 109, 110 of driving the actuator 16, 17 to displace theguide element 14, 15 of the chain 13 in the gear-shifting position.

More specifically, the electronic control unit 40 takes care, in block117, of monitoring the receiving of an end-of-displacement-requestsignal. In the normal ride operating mode, with automatic orsemi-automatic operation, it is the electronic control unit 40 itselfthat generates said end-of-displacement-request signal. Typically, inthe normal ride operating mode with manual control, such a signal is, onthe other hand, generated by the release of the gear-shifting requestcontrol 43-46 by the rider.

When such a signal has been received, if necessary, in a block 115, thestep of obtaining the theoretical position of the second sprocket 11, 12from the information stored in the front and rear memory means 49, 50 iscarried out and then, in block 116, the aforementioned step of drivingthe actuator 16, 17 to displace the chain 13 until the counter 47, 48reaches the theoretical position of the second sprocket 11, 12 iscarried out.

In a third embodiment of the step of stay and repositioning 111, 112,illustrated in FIG. 18, the aforementioned step of driving the actuator16, 17 to displace the guide element 14, 15 of the chain 13 in thetheoretical position of the second sprocket 11, 12 (block 116) issubordinated to the receiving of an end-of-displacement-request signal,in turn subordinated to the passing of a predetermined minimum period oftime after the step 109, 110 of driving the actuator 16, 17 to displacethe guide element 14, 15 of the chain 13 in the gear-shifting position.

More specifically, the electronic control unit 40 takes care, in block118, of activating a timer and, in a block 119, of monitoring thepassing of a predetermined minimum time period Tmin. As for the timer,the considerations outlined above with reference to the embodiment ofFIG. 16 are valid.

When the predetermined minimum time period Tmin has passed, theend-of-displacement-request signal (block 117) is waited for. In manualoperation, it may happen that the release of the control 43-46 by therider already takes place during the passing of the predeterminedminimum time period Tmin (i.e. during the cyclic execution of block 119)and in such a case the electronic control unit 40 will take care ofinhibiting or holding up the end-of-displacement-request signal untilthe predetermined minimum time period Tmin has passed.

Once the two-fold condition that the predetermined minimum time periodTmin has passed and that the end-of-displacement-request signal has beenreceived by the electronic control unit 40 has been met, if necessary(i.e. if step 105 or 106 has not previously been carried out) block 115of obtaining the theoretical position of the second sprocket 11, 12 fromthe information stored in the front and rear memory means 49, 50 iscarried out and then, in block 116, the aforementioned step of drivingthe actuator 16, 17 to displace the chain 13 until the counter 47, 48reaches the theoretical position of the second sprocket 11, 12 iscarried out.

In a fourth embodiment of the step of stay and repositioning 111, 112,illustrated in FIG. 19, the aforementioned step of driving the actuator16, 17 to displace the guide element 14, 15 of the chain 13 in thetheoretical position of the second sprocket 11, 12 (block 116) takesplace once an end-of-displacement-request signal has been received, butsubordinated to the passing of a predetermined minimum period of timeand to the passing of a predetermined maximum period of time. In otherwords, driving step 116 is carried out at the latest in time of thereceiving of end-of-displacement-request signal and the passing of thepredetermined minimum time period if the end-of-displacement-requestsignal is received before the predetermined maximum time period haspassed, or else when the predetermined maximum time period has passed ifthe end-of-displacement-request signal has not yet been received. Insuch a case, the electronic control unit 40 shall ignore theend-of-displacement-request signal received thereafter.

More specifically, the electronic control unit 40 first, in block 120,activates one count-up timer or two count-down timers, one set at apredetermined minimum time period Tmin and the other set at apredetermined maximum time period Tmax.

The electronic control unit 40 then monitors (block 117) the receivingof the end-of-displacement-request signal. While theend-of-displacement-request signal has not been received (output NO ofblock 117), the electronic control unit 40 monitors, in a block 121, thepassing of the predetermined maximum time period Tmax. While thepredetermined maximum time period Tmax has not passed (output NO inblock 121), the electronic control unit continues to monitor thereceiving of the end-of-displacement-request signal (return to block117).

When the predetermined maximum time period Tmax has passed without theend-of-displacement-request signal having been received (output NO ofblock 117 and output YES of block 121), if necessary (i.e. if step 105or 106 has not been carried out previously) the step (block 115) ofobtaining the theoretical position of the second sprocket 11, 12 fromthe information stored in the front and rear memory means 49, 50 iscarried out and then, in block 116, the aforementioned step of drivingthe actuator 16, 17 to displace the chain 13 until the counter 47, 48reaches the theoretical position of the second sprocket 11, 12 iscarried out.

If, on the other hand, the end-of-displacement-request signal isreceived (output YES of block 117) before it has been checked, in theprevious cycle, that the predetermined maximum time period Tmax haspassed, the electronic control unit 40 checks the passing of thepredetermined minimum time period Tmin (block 119).

If the predetermined minimum time period Tmin has not yet passed (outputNO of block 119), the electronic control unit 40 continues to monitorthe passing of such a predetermined minimum time period Tmin remainingat block 119. If, on the other hand, when theend-of-displacement-request signal is received the predetermined minimumtime period Tmin has passed, or as soon as such a period has passed(output YES of block 119), if necessary the step (block 115) ofobtaining the theoretical position of the second sprocket 11, 12 iscarried out and then, in block 116, the step of driving the actuator 16,17 to displace the chain 13 until the counter 47, 48 reaches thetheoretical position of the second sprocket 11, 12 is carried out.

The provision of a predetermined maximum time period Tmax, after thepassing of which the driving step 116 is carried out independently ofthe receiving of the end-of-displacement-request signal, is advantageoussince, as mentioned, an excessive amount of time in the gear-shiftingposition could damage the mechanics of the gearshift 8 and turn out tobe dangerous for the rider.

In a fifth embodiment the step of stay and repositioning 111, 112provides for the checking of the passing of the predetermined maximumtime period Tmax, but not the checking of the passing of thepredetermined minimum time period Tmin. In other words, the block 119 ofFIG. 19 is absent and when the end-of-displacement-request signal hasbeen received, it passes directly to the step of obtaining thetheoretical position of the second sprocket, if necessary (block 115),and to the step of driving the actuator (block 116), as indicated by thedashed arrow in FIG. 19.

In a sixth embodiment the step of stay and repositioning 111, 112provides for the checking of the passing of the predetermined minimumtime period Tmin, but not the checking of the passing of thepredetermined maximum time period Tmax. In other words, the block 121 ofFIG. 19 is absent and until the end-of-displacement-request signal hasbeen received, it remains in block 117, as indicated by the phantomarrow in FIG. 19.

The step of activating the timer(s) 113, 118, 120 can, in alternativeembodiments which are not shown, be carried out before the step 109, 110of driving the actuator 16, 17 to displace the guide element 14, 15 ofthe chain 13 in the gear-shifting position.

The step of stay and repositioning 111, 112 is optional, not just inthat the gear-shifting position for certain pairs of a first and secondsprocket 11, 12 can correspond to the theoretical position of the secondsprocket 11, 12. Indeed, in general the gear-shifting positions differfrom the theoretical positions by sufficiently small amounts (offset oroverstroke) as not to interfere with the correct motion of the bicycle 1in case the chain 14, 15 is left in the gear-shifting position until thenext gear-shifting request.

The sequentiality of the execution of blocks 117, 119, 121 does notnecessarily have to correspond to sequential instructions in the programimplementing the method, these blocks being able to be managed by“interrupts.”

In the various aforementioned embodiments, the values of the theoreticalpositions of the sprockets or of the differential amounts from whichthey derive, the values of the amounts of overstroke and/or the valuesof the gear-shifting positions, as well as the values of the timeperiods of the optional step of stay and repositioning, are preset inthe factory to default values. Preferably, the values listed above, orat least some of them, can however be modified by the user; in such acase it is suitable to provide for the possibility of returning to thedefault values (corresponding to nominal or average values), suitablystored in read-only memory means.

More specifically, the electronically servo-assisted gearshift 8, and inparticular its electronic control unit 40, is suitable to operate,besides in the normal ride operating mode, in other operating modes,including a programming mode of the microprocessor(s) of the electroniccontrol unit 40, a diagnostics mode, a “choice-of-operation mode” inwhich it is possible to choose between manual, automatic orsemi-automatic control of the gearshift, for example as described inU.S. Pat. No. 5,865,454, and a setting mode.

The various operating modes are selected through manual mode selectioncommand means, forming a user interface with the electronic control unit40, preferably in cooperation with the display unit 60. The manual modeselection command means preferably comprise two buttons 61, 62, arrangedat the display unit 60. The user interface can of course comprise otherbuttons or levers, such as the button 63, at the display unit 60 and/orat the grips of the handlebar 70, used in the other operating modes.

For example, when the rider presses the button 61 arranged centrallyunder the display unit 60, the electronic control unit 40 shows on thedisplay unit 60 the various operating modes in cyclical sequence and themode selection means comprises the same button 61 for accepting theoperating mode currently displayed on the display unit 60 and a button,for example the button 62 to the right of the display unit 60, to notaccept it and cause the display of the next operating mode.

Alternatively, the electronic control unit 40 shows on the display unit60 a menu containing all the various operating modes, and the modeselection means comprises a button for scrolling a selection cursorcyclically in the menu, or two buttons to scroll the selection cursor inthe menu in the two directions, as well as a button for accepting theoperating mode upon which the selection cursor is currently displayed.

The buttons for accepting and not accepting the operating mode, or thebuttons for scrolling the cursor, can also be embodied by the sameupwards and downwards gear-shifting request commands 43, 44 or 45, 46,the electronic control unit 40 suitably interpreting the signalgenerated by the pressing of the buttons according to the context, forexample through logic gates or Boolean functions.

A flow chart exemplifying the mode selection of the gearshift 8 isrepresented in FIG. 20. When switched on, 101, the electronic controlunit 40 enters a block 202 for managing the normal ride operating mode,in particular in manual operation. The system remains in this mode, inwhich it waits for and manages the signals coming from the gear-shiftingrequest commands 43-46 in the way above described, negatively answeringto the block 203 querying whether to change the operating mode. In thequery block 203 a mode selection request signal, generated by one of themanual input commands, in particular by the pressing of the button 61,is monitored.

In case the mode selection request signal is activated, output Yes fromthe query block 203, the electronic control unit 40 queries in a block204 whether one wishes to enter into a programming mode and, in theaffirmative case, controls such a mode in a block 205 remaining thereuntil it receives a negative answer to a block 206 requesting whetherone wishes to continue, returning to the block 202 for controlling thenormal ride operating mode. In the case of a negative answer to block204, the electronic control unit 40 queries in a block 207 whether onewishes to enter into a diagnostics mode and, in the affirmative case,controls such a mode in a block 208 remaining there until it receives anegative answer to a block 209 requesting whether one wishes tocontinue, returning to block 202 for controlling the normal rideoperating mode. In the case of a negative answer to block 207, theelectronic control unit 40 queries in a block 210 whether one wishes toenter into the aforementioned operation mode selection and, in theaffirmative case, controls such a mode in a block 211 remaining thereuntil it receives a negative answer to a block 212 requesting whetherone wishes to continue, returning to block 202 for controlling thenormal ride operating mode, in particular in manual, semi-automatic orautomatic operation as chosen by the rider.

The values of the theoretical positions of the sprockets or of thedifferential amounts from which they derive, the values of the amountsof overstroke and/or the values of the gear-shifting positions can becorrected to take into account misalignments with respect to the chain13 of the gearshift group 9, 10 overall and/or misalignments of thesprockets 11, 12 of the gearshift group 9, 10 with respect to eachother, for example as illustrated in U.S. patent application Ser. Nos.10/664,305 and 10/663,231 filed on Sep. 15, 2003 and Sep. 16, 2003respectively. The descriptions of the aforementioned applications arehere incorporated by reference. (The applications have not beenpublished at this time.)

The microprocessor(s) electronic control unit 40 can, for example, bemade in C-MOS technology, which has the advantage of having lowconsumption.

As an alternative to implementation through dedicated hardware, thefunctionalities of the electronic control unit 40 described above can beaccomplished by a software program loadable in a small computer.

1. A method for electronically servo-assisting an electronicallyservo-assisted bicycle gearshift, comprising the steps of: a) receivinga signal requesting a displacement of a chain of a bicycle gearshiftfrom a first sprocket to a second adjacent sprocket of a gearshift groupcomprising at least two sprockets, b1) if the first sprocket has asmaller diameter than the second sprocket, obtaining an upwardsgear-shifting position for the second sprocket, b2) if the firstsprocket has a larger diameter than the second sprocket, obtaining adownwards gear-shifting position for the second sprocket, and c) drivingan actuator of the gearshift group in response to the signal to displacea guide element of the chain in an axial direction with respect to thegearshift group from the first sprocket to the upwards gear-shiftingposition for the second sprocket or to the downwards gear-shiftingposition for the second sprocket, respectively.
 2. The method of claim 1wherein the upwards gear-shifting position for the second sprocket andthe downwards gear-shifting position for the second sprocket aresubstantially asymmetrically distant from a theoretical position of thesecond sprocket.
 3. The method of claim 1 wherein the step b1) ofobtaining the upwards gear-shifting position for the second sprocketcomprises the step of: b11) obtaining a theoretical position of thesecond sprocket.
 4. The method of claim 3 wherein the step b1) ofobtaining the upwards gear-shifting position for the second sprocketalso comprises the step of: b12) algebraically adding a predeterminedamount of overstroke to the theoretical position for the secondsprocket.
 5. The method of claim 1 wherein the step b2) of obtaining thedownwards gear-shifting position for the second sprocket comprises thestep of: b21) obtaining a theoretical position of the second sprocket.6. The method of claim 5 wherein the step b2) of obtaining the downwardsgear-shifting position for the second sprocket also comprises the stepof: b22) algebraically adding a predetermined amount of overstroke tothe theoretical position of the second sprocket.
 7. The method of claim1 further comprising the sequential steps of: c1) temporarilymaintaining the position of the chain guide element obtained in step c),and d) driving the actuator of the gearshift group to displace the chainguide element in the axial direction with respect to the gearshift groupfrom the gear-shifting position to a theoretical position of the secondsprocket.
 8. The method of claim 7 wherein the step c1) of temporarilymaintaining the position comprises the step of: e) waiting apredetermined time period.
 9. The method of claim 7 wherein the step c1)of temporarily maintaining the position comprises the step of: f)waiting for an end-of-displacement-request signal.
 10. The method ofclaim 7 wherein the step c1) of temporarily maintaining the positioncomprises the sequential steps of: g) waiting a predetermined minimumtime period, and f) waiting for an end-of-displacement-request signal.11. The method of claim 7 wherein the step c1) of temporarilymaintaining the position comprises the steps of: h) monitoring thepassing of a predetermined minimum time period, i) monitoring thereceiving of an end-of-displacement-request signal, wherein theexecution of step d) takes place at the latest in time between thereceiving of the end-of-displacement-request signal and the passing ofthe predetermined minimum time period.
 12. The method of claim 7 whereinthe step c1) of temporarily maintaining the position comprises the stepsof: i) monitoring the receiving of an end-of-displacement-requestsignal, j) monitoring the passing of a predetermined maximum timeperiod, wherein the execution of step d) takes place at the first intime between the receiving of the end-of-displacement-request signal andthe passing of the predetermined maximum time period.
 13. The method ofclaim 7 wherein the step c1) of temporarily maintaining the positioncomprises the steps of: h) monitoring the passing of a predeterminedminimum time period, i) monitoring the receiving of anend-of-displacement-request signal, j) monitoring the passing of apredetermined maximum time period, wherein the execution of step d)takes place at the latest in time between the receiving of theend-of-displacement-request signal and the passing of the predeterminedminimum time period if the receiving of the end-of-displacement-requestsignal precedes in time the passing of the predetermined maximum timeperiod, or upon the passing of the predetermined maximum time period ifit precedes the receiving of the end-of-displacement-request signal. 14.The method of claim 1 further comprising a step of setting a value ofeach of said or each gear-shifting positions or of said or of each ofsaid amounts of overstroke and/or of said or of each of saidpredetermined time periods.
 15. A program for electronicallyservo-assisting a bicycle gearshift, comprising program code meanssuitable for carrying out the steps of the method of claim 1 when theprogram is run on a computer, embodied in at least one microcontroller.16. An electronic circuit suitable for carrying out the steps of themethod of claim
 1. 17. A program for electronically servo-assisting abicycle gearshift, the program being run on a computer and comprisingthe following steps: a) receiving a signal requesting a displacement ofa chain of a bicycle gearshift from a first sprocket to a secondadjacent sprocket of a gearshift group comprising at least twosprockets, b1) if the first sprocket has a smaller diameter than thesecond sprocket, obtaining an upwards gear-shifting position for thesecond sprocket, b2) if the first sprocket has a larger diameter thanthe second sprocket, obtaining a downwards gear-shifting position forthe second sprocket, and c) driving an actuator of the gearshift groupin response to the signal to displace a guide element of the chain in anaxial direction with respect to the gearshift group from the firstsprocket to the upwards gear-shifting position for the second sprocketor to the downwards gear-shifting position for the second sprocket,respectively.
 18. An electronic circuit that carries out the followingsteps: a) receiving a signal requesting a displacement of a chain of abicycle gearshift from a first sprocket to a second adjacent sprocket ofa gearshift group comprising at least two sprockets, b1) if the firstsprocket has a smaller diameter than the second sprocket, obtaining anupwards gear-shifting position for the second sprocket, b2) if the firstsprocket has a larger diameter than the second sprocket, obtaining adownwards gear-shifting position for the second sprocket, and c) drivingan actuator of the gearshift group in response to the signal to displacea guide element of the chain in an axial direction with respect to thegearshift group from the first sprocket to the upwards gear-shiftingposition for the second sprocket or to the downwards gear-shiftingposition for the second sprocket, respectively.
 19. A method forelectronically servo-assisting an electronically servo-assisted bicyclegearshift, comprising the steps of: a) receiving a signal requesting adisplacement of a chain of a bicycle gearshift from a first sprocket toa second sprocket of a gearshift group comprising at least twosprockets, b1) if the first sprocket has a smaller diameter than thesecond sprocket, obtaining an upwards gear-shifting position for thesecond sprocket through: b11) obtaining a theoretical position of thesecond sprocket, and b12) adding a predetermined amount of overstroke tothe theoretical position for the second sprocket, b2) if the firstsprocket has a larger diameter than the second sprocket, obtaining adownwards gear-shifting position for the second sprocket, and c) drivingan actuator of the gearshift group in response to the signal to displacea guide element of the chain in an axial direction with respect to thegearshift group from the first sprocket to the upwards gear-shiftingposition for the second sprocket or to the downwards gear-shiftingposition for the second sprocket, respectively.
 20. A method forelectronically servo-assisting an electronically servo-assisted bicyclegearshift, comprising the steps of: a) receiving a signal requesting adisplacement of a chain of a bicycle gearshift from a first sprocket toa second sprocket of a sprocket set, b1) if the first sprocket has asmaller diameter than the second sprocket, obtaining an upwardsgear-shifting position for the second sprocket through: b11) obtaining atheoretical position of the second sprocket, and b12) adding apredetermined amount of overstroke to the theoretical position for thesecond sprocket, b2) if the first sprocket has a larger diameter thanthe second sprocket, obtaining a downwards gear-shifting position forthe second sprocket, and c) driving an actuator in response to thesignal to displace a guide element of the chain in an axial directionwith respect to the sprocket set from the first sprocket to the upwardsgear-shifting position for the second sprocket or to the downwardsgear-shifting position for the second sprocket, respectively.